1. Field of the Invention
This invention relates generally to gaming machines such as slot machines, ball-shooting game machines, poker game machines, and the like, and more particularly, to a gaming machine having a variable display for displaying a plurality of symbols that correspond to mechanically driven reels, or electrically-operated display means such as liquid crystal displays (LCDs), light emitting diodes (LEDs), cathode ray tubes (CRTs), or the like.
2. Description of the Prior Art
In a conventional slot machine, a rotating reel functions as a variable display. One or more such reels, illustratively three reels in a known arrangement, are provided with a plurality of symbols (e.g., twenty-two symbols) on peripheral surfaces thereof and are urged into rotation by a drive arrangement that may include a stepping motor. In use, the plural reels are caused to be rotated and a "win" is determined in response to a particular combination of symbols positioned on a predetermined winning line when the rotation of the reels ceases. Upon determining the occurrence of a win, coins or medals are paid out in a number or value that corresponds to the characteristic of the win.
In a gaming machine of the type that produces displays that vary with the multiplicity of combinations of the plurality of symbols as mentioned above, the variable displays are controlled by a control unit that consists of electronic circuitry, such as a microcomputer or the like, whereby the probability of a win is not greatly influenced by the skill of a player.
More particularly, in the case of the slot machine, when the player operates a lever or pushes a start button, the control unit drives the reels of the variable display into rotation, and samples a random number value. In response to the sampled random number value, the control unit determines the symbols (i.e.., stop symbols) that are displayed in display windows when the reels are stopped. Then, the control unit stops rotation of the reels in response to stop operations by the player or after a predetermined time period has passed. Afterward, the control unit performs win determination procedure.
In ball-shooting game machines, such as pachinko machines and the like, instead of operating the lever or pushing the start button as above, the control unit actuates a variable display and samples a random number value when a game ball has entered a winning zone called the "start hole." Then, depending upon the sampled value and the content of a winning table, the control unit determines whether the play is a win and also determines the stop symbols. The control unit controls the variable displays to stop after a predetermined time period has passed.
In a gaming machine comprising a variable display of video type (e.g., CRTs), graphical data corresponding to patterns of symbols is stored in a memory (symbol ROM) in accordance with a predetermined arrangement. The control unit reads the graphical data that is to be displayed at the variable display, from the symbol ROM.
When playing such gaming machines, the player can readily determine whether the play is a win or a loss, the number of play balls (prize) to be paid out for the player being determinable by viewing the plurality of symbol rows after they have been stopped. Therefore, the player watches the displays when each of the symbol rows is stopped, with significant interest.
In the above-mentioned gaming machines, the payout rate of the coins, determined in response to the odds of winning, is established with the probability that any particular combination of stop symbols will stand when the rotation of the plurality of reels that form the variable display ceases and the number of the coins to be paid out therefor. Thus, the player is greatly interested in the setting of the odds of winning, and the setting thereof is a significant consideration for the gambling establishment, as it ultimately affects the availability of the gaming machines and the resulting profitability of the business.
The odds of winning in gaming machines of the type that control the payout of coins in response to the random number sampling, as is the case in the gaming machines of the type wherein a stop symbol combination is determined with the use of a win determination table (stored in ROM) including winning symbol combinations having respectively associated probabilities of occurring, may be set by the gambling establishment as desired within a regulated range. Such is the case with slot machines employed in pachinko halls in Japan.
With respect to slot machines of the type generally used in the United States, the odds of winning, pursuant to regulations, cannot be modified freely after the slot machine has been installed in the gambling establishment. In addition, the probabilities associated with symbol combinations corresponding to a loss, as well as those corresponding to a win, must be calculated and the odds of occurrence must correspondingly be controlled. Thus, if the above method is employed, the control procedure becomes more complicated and operation time becomes longer. Therefore, in such slot machines, a known method of operation, described in U.S. Pat. No. 4,448,419, employs a table of probabilities correlated to the symbols of each reel, whereby the probability of occurrence of each symbol for each reel is determined in response to a random number value sampled by a random number sampling procedure. A table (stored in ROM) for each reel is thus referred to as a "virtual reel." The virtual reel is arranged to correspond to symbols similar to those on an actual reel sheet, but the number of symbols is different from an actual reel.
In gaming machines that employ the technique of the virtual reel, only a single combination of virtual reels is stored from which the stop symbols are determined in response to the random number sampling. Thus, after the gaming machines have been installed in the gambling establishment, as a player plays the game, the manner in which the stop symbols appear is decided, i.e., a pattern of standing of combinations of the stop symbols is getting decided, and the game becomes monotonous to make the player tired.